Conventionally, there is proposed a technique for applying a transmission-type screen equipped with a microlens array to a head-up display and a laser projector. Using such a transmission-type screen is more preferable than using a diffuser panel because an influence caused by the speckle noise can be suppressed. For example, in Patent Reference-1, there is proposed an image forming device including a laser projector and a microlens array on which plural microlenses are arranged. In Patent Reference-2, there is proposed a technique of determining the pitch of each microlens so that the width of the diffraction of beam diffused by each microlens of a microlens array is equal to or shorter than the pupil diameter of the observer thereby to prevent the irregular brightness due to the uncertainty that the peak of the diffracted light diffused at the microlens enters the pupils of an observer.